Earth’s Future REVIEW Stratigraphic and Earth System approaches to defining the 10.1002/2016EF000379 Anthropocene Will Steffen1,2, Reinhold Leinfelder3, Jan Zalasiewicz4, Colin N. Waters5, Mark Williams4, Colin Key Points: Summerhayes6, Anthony D. Barnosky7, Alejandro Cearreta8, Paul Crutzen9, Matt Edgeworth10,Erle • Stratigraphy and Earth System 11 12 13 14 15 science have built a multidisciplinary C. Ellis , Ian J. Fairchild , Agnieszka Galuszka , Jacques Grinevald , Alan Haywood , Juliana Ivar approach for understanding Earth do Sul16, Catherine Jeandel17, J.R. McNeill18, Eric Odada19, Naomi Oreskes20, Andrew Revkin21, evolution, including the advent of Daniel deB. Richter22, James Syvitski23, Davor Vidas24, Michael Wagreich25,ScottL.Wing26, the Anthropocene. 27 28 • Both approaches provide strong Alexander P.Wolfe , and H.J. Schellnhuber evidence that human activities have 1 2 pushed the Earth into the Fenner School of Environment and Society, The Australian National University, Acton, Australia, Stockholm Resilience Anthropocene, starting from the Centre, Stockholm University, Stockholm, Sweden, 3Department of Geological Sciences, Freie Universität Berlin, Berlin, mid-20th century. Germany, 4Department of Geology, University of Leicester, Leicester, UK, 5British Geological Survey, Nottingham, UK, • Potential scenarios for the future 6Scott Polar Research Institute, Cambridge University, Cambridge, UK, 7Jasper Ridge Biological Preserve, Stanford Anthropocene range from more 8 intense interglacial conditions to a University, Stanford, California, USA, Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, 9 greenhouse state with much less Universidad del País Vasco UPV/EHU, Bilbao, Spain, Department of Atmospheric Chemistry, Max-Planck-Institute for polar ice. Chemistry, Mainz, Germany, 10School of Archaeology and Ancient History, University of Leicester, Leicester, UK, 11Department of Geography and Environmental Systems, University of Maryland–Baltimore County, Baltimore, 12 Corresponding author: Maryland, USA, School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK, 13 W. Steffen, will.steff[email protected] Geochemistry and the Environment Division, Institute of Chemistry, Jan Kochanowski University, Kielce, Poland, 14Institut de Hautes Études Internationales et du Développement, Geneva, Switzerland, 15School of Earth and Environment, University of Leeds, Leeds, UK, 16Institute of Oceanography, Federal University of Rio Grande, Rio Grande, Citation: 17 Steffen, W. et al. (2016), Stratigraphic Brazil, Laboratoire d’Etudes en Géophysique et Océanographie Spatiales (CNRS, Centre National d’Études Spatiales, 18 and Earth System approaches to Institut de Recherche pour le Développement, Toulouse, France, History Department, Georgetown University, defining the Anthropocene, Earth’s Washington, District of Columbia, USA, 19Department of Geology, University of Nairobi, Nairobi, Kenya, 20Department Future, 4, 324–345, of the History of Science, Harvard University, Cambridge, Massachusetts, USA, 21Dyson College Institute for doi:10.1002/2016EF000379. Sustainability and the Environment, Pace University, Pleasantville, New York, USA, 22Nicholas School of the Environment, Duke University, Durham, North Carolina, USA, 23Department of Geological Sciences, University of Received 27 APR 2016 Colorado–Boulder, Boulder, Colorado, USA, 24Marine Affairs and Law of the Sea Programme, The Fridtjof Nansen Accepted 15 JUL 2016 Institute, Lysaker, Norway, 25Department of Geodynamics and Sedimentology, University of Vienna, Vienna, Austria, Accepted article online 20 JUL 2016 26 Published online 12 AUG 2016 Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, USA, 27Department of Biological Sciences, University of Alberta, Edmonton, Canada, 28Potsdam Institute of Climate Impact Research, Potsdam, Germany Abstract Stratigraphy provides insights into the evolution and dynamics of the Earth System over its long history. With recent developments in Earth System science, changes in Earth System dynamics can now be observed directly and projected into the near future. An integration of the two approaches provides powerful insights into the nature and significance of contemporary changes to Earth. From both perspectives, the Earth has been pushed out of the Holocene Epoch by human activities, with the mid-20th century a strong candidate for the start date of the Anthropocene, the proposed new epoch in Earth history. Here we explore two contrasting scenarios for the future of the Anthropocene, recognizing that the Earth System has already undergone a substantial transition away from the Holocene state. A rapid shift of societies toward the UN Sustainable Development Goals could stabilize the Earth System in a state with more intense interglacial conditions than in the late Quaternary climate regime and with little further biospheric change. In contrast, a continuation of the present Anthropocene trajectory of growing human pressures will likely lead to biotic impoverishment and a much warmer climate with a © 2016 The Authors. significant loss of polar ice. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distri- bution in any medium, provided the 1. Introduction original work is properly cited, the use is non-commercial and no modifica- The Anthropocene, the proposed new geological epoch in Earth history [Crutzen and Stoermer, 2000; tions or adaptations are made. Crutzen, 2002; Zalasiewicz et al., 2008], is challenging many areas of research in a variety of ways. The STEFFEN ET AL. DEFINING THE ANTHROPOCENE 324 Earth’s Future 10.1002/2016EF000379 term and concept have been discussed within diverse disciplines in the natural sciences [e.g., Ellis et al., 2012; Gillings and Paulsen, 2014; Capinha et al., 2015; Corlett, 2015; Williams et al., 2015] and in the envi- ronmental humanities and social sciences [e.g., Chakrabarty, 2009; Vidas, 2011; Malm and Hornborg, 2014; Fischer-Kowalski et al., 2014; Bai et al., 2015; Latour, 2015; Vidas et al., 2015; Bonneuil and Fressoz, 2016], with more interdisciplinary approaches also appearing [Braje, 2015; Latour, 2015; Maslin and Lewis, 2015]. Although the proposal was initiated in the Earth System science community [Crutzen and Stoermer, 2000; Steffen, 2013; see Revkin, 1992 for an earlier proposed “Anthrocene”], recognition of the Anthropocene as an epoch following the Holocene necessitates that the proposal be grounded in the Geologic Time Scale, one of the cornerstones of geology. Subsequently, much work [Zalasiewicz et al., 2015; Waters et al., 2016 and references therein] has focused on testing whether the stratigraphic record of the Anthropocene is adequate for the formal definition of a new epoch following the protocols of the International Commission on Stratigraphy and its parent body, the International Union of Geological Sciences. The result of this work has been a convergence of evidence and information obtained from Earth System science and from stratigraphy. Here we examine this convergence of approaches to define the Anthro- pocene, highlighting their changing relationship through time and the insights that each brings to examine the dynamics of the Earth System. 2. Historical Relationship Between Stratigraphy and Earth System Science Earth System science is a highly interdisciplinary enterprise that aims to build a holistic understanding of our evolving planet [Lenton, 2015]. It arrived on the research landscape very recently (primarily since the 1980s), and some scholars have suggested that it represents an emerging paradigm [Malone and Roederer, 1985; ICSU, 1986; Grinevald, 1987; Hamilton and Grinevald, 2015]. Earth System science builds on the long history of advances in the geosciences [Oldroyd, 1996; Bard, 2004; Galvez and Gaillardet, 2012] and on more recent system-level thinking applied to the climate and the biosphere [Budyko, 1986; Clark and Munn, 1986; NASA, 1988; Rambler et al., 1989]. An early pioneer of this holistic approach, following Alexander von Humboldt, was the Russian min- eralogist and naturalist Vladimir I. Vernadsky, one of the founders of geochemistry and the creator of biogeochemistry [Vernadsky, 1924; 1929; 1998]. Vernadsky’s research on biogeochemistry was central to the rise of Earth System science, and to the scientific study of Earth’s biosphere in general [Grinevald, 1987; Polunin and Grinevald, 1988; Smil, 2002; Jørgensen, 2010], including humanity as a new geological agent [Vernadsky, 1924; 1945; 1998]. Vernadsky’s pioneering work largely languished for several decades, but global biogeochemical cycles reappeared prominently in the 1970s when James Lovelock, the father of the Gaia hypothesis, provided a complementary conceptual framework for the Earth as a system [Lovelock and Margulis, 1974; Lovelock, 1979; 1988]. Contemporary Earth System science draws on a wide range of new tools and disciplinary expertise for directly observing and modeling the dynamics of the Earth System (cf. section 4), emphasizing the conceptual framework of complex-systems science, hence the emphasis on System in its name. The Earth System is usually defined as a single, planetary-level complex system, with a multitude of inter- acting biotic and abiotic components, evolved over 4.54 billion years and which has existed in well-defined, planetary-level states with transitions between them